As a systematic process, treatment of sludge water often involves a number of systems such as a collection system, separation system, dewatering system and monitoring system. Nowadays a sludge water separation system has become a key part in water reuse and solid waste reduction.
Traditional sludge water treatment technologies can be classified into two categories based on their fundamental mechanisms: physical treatment and physic-chemical treatment. Screening, grit chamber, gravity sedimentation, filtration and centrifugal separation are typical physical treatment methods. Physic-chemical treatment includes chemical coagulation and sedimentation, clarification, floatation and membrane filtration.
In conventional water treatment plants, chemical coagulation and sedimentation treatment with traditional sedimentation tanks are commonly used because they are very cost-effective. In some situations, inclined plate settler is used as replacement of gravity sedimentation tank in order to increase the treatment efficiency and decrease the infrastructure footprint. Clarified water is pumped back to water treatment system for further treatment, while the sludge is sent to thickening and dewatering station.
However, in the above process, space required for gravity sedimentation tank, as the key unit in the process, is large due to the relatively low overflow rate of 1-2 m3/m2·h. Meanwhile, the settle sludge contains 97%-99% water, and the clarified water in gravity sedimentation tank contains more than 70 ppm suspended solid. This is beyond the water reuse standard as well as water discharge standard. Plus, the treatment efficiency is worse when there is a large amount of cation in the water.
In light of the above, a need exists for a new method and device to treat the sludge water, decrease suspended solid in the treated water and fulfill the water reuse purpose more efficiently.